Re: [LAU] jdelay - measured latency of a usb interface

On Tue, Mar 24, 2009 at 11:39:03PM -0700, Ken Restivo wrote: Yes, there is a lower bound. It depends on the protocol version being used. Also, don't blindly believe the latency values displayed, as these may be estimates. If you have the means, measure the latency using external analysis. -- Diversion. We've been reading about USB latency in the past couple of days on the One Laptop Per Child project, where USB to Ethernet devices are attached to tiny school servers. If you'd like to follow the technical details ... Problem statement: http://lists.laptop.org/pipermail/devel/2009-March/023887.html Solution: http://lists.laptop.org/pipermail/server-devel/2009-March/003105.html (it was a USB 1.1 device) And for the truly interested, the wireless chipset is also on USB, and the Linux kernel appears to do half the possible data rate, given that the OpenFirmware can achieve so much more with full control of the hardware: http://lists.laptop.org/pipermail/devel/2009-March/023899.html (the data rate that is achieved by the kernel is well within the needs of the target market though). -- James Cameron mailto:quozl@us.netrek.org http://quozl.netrek.org/